Blood continues to stain the sands of the Middle East. There are the well-known civil wars in Syria, Iraq and Libya, along with terror incidents in Egypt, Israel, Lebanon and elsewhere. Less attention is paid to the creeping conflict in Yemen, where Saudi Arabia and Iran are fighting a proxy war that threatens to descend into full-scale war and suck in other countries, including the United States. A three-day ceasefire was attempted last week but it expired without halting the fighting. Reinvigorated diplomacy that will culminate in a power-sharing agreement is needed to halt the slide to civil war and avert a humanitarian catastrophe.

Yemen is a relatively young state, formed in 1992 when the Yemen Arab Republic of the north and the People’s Democratic Republic of Yemen in the south unified. President Ali Abdullah Saleh was forced out in 2011 as the political situation deteriorated and he handed over power to Abd Rabbuh Mansur Hadi. The transition did not quell the violence and Saleh, backed by Houthi rebels that enjoyed support from Iran, decided that his abdication was a mistake. He and his allies won back the capital, Sanaa, in 2014. Hadi did not give up, however; with backing from the government of Saudi Arabia, his forces took control of the key commercial port of Aden and territory in southern Yemen. It is estimated that nearly 10,000 people have died in the fighting, almost half civilians.

The domestic struggle is now a proxy war between Iran and Saudi Arabia, which means that the U.S. is also involved as an ally of Riyadh. While Washington is concerned about the spread of Iranian influence in the region, it is not as worried as Saudi Arabia, which sees its struggle with Iran as a zero-sum contest. Nevertheless, the U.S. backs the Saudi government to reduce concern in Riyadh about a tilt in American thinking in the aftermath of the Iranian nuclear deal, which the Saudis opposed, as well as to secure Saudi support for the fight against Islamic State radicals in Iraq and Syria.

The U.S. also worries about the strength of al-Qaida on the Arabian Peninsula. In the past, it has operated in southern Yemen and while the Saudi-backed forces now control much of that territory, it enjoys a relatively safe haven in the area between the two fighting forces. Until last year, the U.S. operated special operations out of the north but those efforts have been scaled back as the civil war intensified. Now, U.S. and Saudi forces operate more closely together, and their entanglement risks widening the conflict.

Earlier this month, Saudi forces attacked a funeral in Sanaa that a key politician was thought to be attending. More than 140 people were killed and hundreds of others wounded. This horrific strike was only the exclamation point on an increasingly brutal air campaign that has had terrible humanitarian consequences. The Saudis blamed the Houthis for using civilian facilities as shields for their military, but that rationalization had run its course. After the attack on the funeral, Houthi forces responded with two missile attacks on U.S. naval vessels in the area, which missed. The U.S. retaliated with three missile strikes on radar facilities in Yemen.

The escalation of the violence has been sobering. It prompted U.N. envoys to broker a three-day ceasefire. That proved to be a ceasefire more in name than fact, with both sides violating the accord at will. The Hadi government accused the Houthis of nearly 1,000 mortar and armed attacks in the last 24 hours of the ceasefire alone. Hopes that the original agreement could be extended were dashed, but while the Houthis seek a negotiated settlement to the conflict, they seem unwilling to continue the truce.

That process may get a boost from the U.S., which is increasingly concerned about being sucked into war. U.S. officials have gone to pains to note that cruise missile strikes on the radar facilities do not indicate support for coalition operations in Yemen at large or in the Red Sea, adding that the U.S. is “not intending to be brought into the war in any fashion.” They were, as U.S. President Barack Obama explained, “limited and proportionate strikes” and acts of self-defense.

It’s unclear how much influence the U.S. has over Saudi Arabia’s decision-making in a theater so close to the latter. But it is equally uncertain whether Riyadh can prosecute the war without U.S. support and that may be the lever that prompts renewed diplomacy. Riyadh retains leverage of its own. It has imposed a blockade on Yemen that threatens a humanitarian crisis: according to the United Nations, half of Yemen’s population, or some 14 million people, do not have enough to eat.

A power-sharing arrangement between Hadi and Saleh is the only sustainable solution, but that requires Saudi Arabia to acknowledge Iranian influence in Yemen. But influence is not the same as control. Saudi Arabia should back a deal that empowers Yemeni nationalists who will be equidistant from Riyadh and Tehran. That is the best deal for all sides in the Yemen conflict, as well as the parties that back them.